Is a blood transfusion safe?

Blood used for
transfusions in the United States is very safe and generally free from disease.
Donated blood is carefully tested and tracked. It is very rare to get a disease through a
blood transfusion.

Getting the wrong blood type by accident is the
main risk in a blood transfusion, but it is rare. For every 1 million units of blood transfused, getting the wrong blood type happens, at the most, 4 times.1
Transfusion with the wrong blood type can cause a severe reaction that may be
life-threatening.2

Some people bank their own blood a few weeks
before they have surgery. If they need a transfusion during surgery, they can
receive their own banked blood. This reduces the risk of disease and
transfusion reaction from donated blood.

If you have many blood
transfusions, you are more likely to have problems from
immune system reactions. A reaction causes your
body to form antibodies that attack the new blood cells. But tests can help
avoid this. Before you get a blood transfusion, your blood is tested to find
out your blood type. And the blood you will get in the transfusion is tested to
make sure it matches your blood.

You may have a mild allergic
reaction even if you get the correct blood type. Signs of a reaction
include:

A
fever.

Hives.

Shortness of
breath.

Pain.

A fast heart
rate.

Chills.

Low blood pressure.

A mild reaction can be scary, but it rarely is dangerous
if it's treated quickly.

What are blood types, and why are they important?

The most important blood type classification systems are the ABO system and the
Rh system. A, B, AB, and O are the
blood types in the ABO system. Each type of blood in
the ABO system also has a positive or negative
Rh factor. For example, if you have "A+ blood," it
means your blood is type A in the ABO system and your Rh factor is
positive.

If you get blood in a transfusion that isn't the right
type, you may have a transfusion reaction. A mild transfusion reaction rarely
is dangerous, but you must get treatment quickly. A severe transfusion reaction
can be deadly.

How is blood collected?

Blood banks collect blood
from volunteer donors. Before they donate, volunteers must answer questions
about their current health, health history, and any diseases they may have been
exposed to through travel to foreign countries, sexual behavior, drug use, or needle sticks (such as from tattoos).
Only people who pass this survey are allowed to donate blood.

Donated blood is then carefully tested for certain diseases and to find
out the blood type. If there is any chance that the blood may not be safe to
use, it is thrown away.

Most blood that passes the tests is then
split into its components and sent out for use.

Blood and its
components can be stored or used for only a short time before they must be
thrown away. This is why blood banks are always looking for donors.

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Uses of Blood Transfusion

Transfusions
are used to treat blood loss or to supply blood components that your body
cannot make for itself.

Treating blood loss

Blood loss may result from
injury, major surgery, or diseases that destroy
red blood cells or
platelets, two important blood components. If too much
blood is lost (low blood volume), your body cannot maintain a proper blood
pressure, which results in
shock. Blood loss can also reduce the number of
oxygen-carrying red blood cells in the blood, which may prevent enough oxygen
from reaching the rest of the body.

Whole blood is rarely given
to treat blood loss. Instead, you are given the blood component you most need.
If you have lost too many red blood cells or are not making enough of them, you
are given packed red blood cells. If you have low blood volume, you are given
plasma and/or other fluids to maintain blood pressure.
If you have lost a great deal of blood, or if your
clotting factors or platelets are low or abnormal, you
may also need a transfusion of either of these to help control bleeding.
Sometimes you may need replacements of some blood substances if your body does
not make enough of them. For example, you may be given substances to help your
blood clot (clotting factors) if you do not have enough of them
naturally.

Blood lost during surgery sometimes can be recovered,
cleaned, and returned to you as a transfusion. This greatly reduces the amount
of blood you might otherwise need to receive. Receiving your own blood back is
safer, because there is no chance of a reaction.

Replacing or supplementing blood components

One blood
component that affects the blood's ability to clot is platelets. A reduced
number of platelets (thrombocytopenia) or the failure of
platelets to function properly increases the time it takes for bleeding to stop
(increased bleeding time). Transfusion with platelets improves the clotting
time, which reduces the risk of uncontrolled bleeding. This treatment does not cure
the cause of platelet loss.

Anemia is a
decrease in the number of oxygen-carrying red blood cells or a decrease in the
amount of
hemoglobin, the oxygen-carrying substance in the red
blood cells. There are several types of anemia, each with a different cause,
and each is treated differently. Severe anemia may be treated with a
transfusion of packed red blood cells. This temporarily increases the
number of oxygen-carrying red blood cells in circulation and may improve
symptoms, but it does not treat the cause of the anemia.

Blood Donation

Almost all of the blood used for blood transfusions is donated by volunteers.

Safety of donated blood

The process of blood donation and the handling of donated
blood in the United States is regulated by the U.S. Food and Drug
Administration (FDA). The FDA enforces five layers of overlapping safeguards to
protect the blood supply against disease.

Donor screening. To
donate blood, you must answer a series of questions about your current health,
health history, any travel to countries where certain diseases are common, and
behavior that increases your risk for getting certain diseases, such as drug
use or unprotected sex. Your temperature, your blood pressure, and the volume
of red blood cells in a blood sample (hematocrit) are
checked. You may not be allowed to donate blood if any of these screening steps
suggests a problem, such as potential exposure to an infectious disease or
anemia.

Deferred-donor lists. Organizations that collect blood must keep lists of people who
are permanently prevented from giving blood. Potential donors must be checked
against this list so that blood is not collected from them. The deferred-donor
list includes people who have had certain types of cancer, had
hepatitis after age 11, or are at high risk for
HIV infection.

Blood testing. After donation, every unit of blood is tested for certain diseases, such as hepatitis B and C, HIV, West Nile virus, syphilis, and
HTLV-I/II viruses. If any disease is detected, the blood is thrown away.

Quarantine. Donated blood is kept isolated
from other blood and cannot be used for any purpose until it passes all
required tests.

Quality assurance. Blood
centers must keep careful records of every unit of donated blood. If a problem
arises involving a donated unit of blood, the blood center must notify the FDA
and work with them to correct the problem.

Donating blood for your own use

If you are going
to have surgery and expect to need a
blood transfusion, you may want to consider donating
or banking your own blood before the surgery (autologous donation).

Blood Types

Your blood is
typed, or classified, according to the presence or
absence of certain markers (antigens) found on red blood cells and
in the plasma that allow your body to recognize blood as its own. If another
blood type is introduced, your
immune system recognizes it as foreign and attacks it,
resulting in a
transfusion reaction.

ABO blood type system

The ABO system consists of
A, B, AB, and O blood types. People with type A have
antibodies in the blood against type B. People with
type B have antibodies in the blood against type A. People with AB have no
anti-A or anti-B antibodies. People with type O have both anti-A and anti-B
antibodies. People with type AB blood are called universal recipients, because
they can receive any of the ABO types. People with type O blood are called
universal donors, because their blood can be given to people with any of the
ABO types. Mismatches with the ABO and Rh blood types are responsible for the
most serious, sometimes life-threatening, transfusion reactions. But these types of reactions are rare.

For every 1 million units of blood transfused, getting the wrong blood type happens, at the most, 4 times.1
Transfusion with the wrong blood type can cause a severe reaction that may be
life-threatening.2

Rh system

The Rh system classifies blood as
Rh-positive or Rh-negative, based on the presence or absence of Rh antibodies
in the blood. People with Rh-positive blood can receive Rh-negative blood, but
people with Rh-negative blood will have a transfusion reaction if they receive
Rh-positive blood. Transfusion reactions caused by mismatched Rh blood types
can be serious.

Minor blood types

There are over 100 other blood
subtypes. Most have little or no effect on blood transfusions, but a few of
them may be the main causes of mild transfusion reactions. Mild transfusion
reactions are frightening, but they are rarely life-threatening when treated
quickly.

Risks of Blood Transfusion

Immune-related (transfusion) reactions

Immune-related reactions
occur when your immune system attacks components of the blood being transfused
or when the blood causes an
allergic reaction. This is called a transfusion reaction.

Most transfusion
reactions occur because of errors made in matching the recipient's blood to the
blood transfused. These errors are very rare, and much effort is made to prevent them.

Even receiving the correct blood type sometimes results in a transfusion
reaction. These reactions may be mild or severe. Most mild
reactions are not life-threatening when treated quickly. Even mild reactions,
though, can be frightening.

Doctors will stop a blood transfusion if they think you are having a
reaction. A reaction may turn out to be mild. But at the beginning, it is hard
for doctors to know whether it will be severe.

There are several immune-related transfusion
reactions.

Nonhemolytic fever reactions cause fever and chills without
destruction (hemolysis) of the red blood cells. This is the most common
transfusion reaction. It can occur even when the blood has been correctly
matched and administered. The more transfusions you receive, the greater your
risk for this type of reaction. People who have had several transfusions are
more likely to have nonhemolytic fever reactions or other types of
immune system reactions. These problems occur because
the body mistakes the new blood as harmful and makes specific
antibodies to destroy it. Careful screening helps
reduce the risk for these problems.

Hemolytic transfusion reactions can cause the most serious problems, but these are rare. These reactions can occur when your ABO or Rh
blood type and that of the transfused blood do not
match. If this happens, your immune system attacks the transfused red
blood cells. This can be life-threatening.

Mild hemolytic transfusion reactions can happen when there is a mismatch of one of the more than 100
minor blood types. Most of the time, these reactions
to the minor blood types are less serious than a mismatch of the ABO or Rh blood types.

An
immune reaction to
platelets in transfused blood results in the
destruction of the transfused platelets. People who have this type of
reaction may have trouble finding blood that can be transfused without
causing a reaction.

In rare cases, an immune reaction may take
place that attacks the person's lungs (transfusion-related acute lung injury).
This results in trouble breathing and other symptoms. Most people recover
fully from this type of reaction.

Nonimmune reactions

Fluid overload is a common
type of nonimmune reaction.

Fluid overload can occur when you receive too
much fluid through transfusions, especially if you have not experienced blood
loss before the transfusion.

Fluid overload may require treatment
with medicines to increase urine output (diuretics) to rid your body of the
excess fluid.

A person can develop iron overload after
having many repeated blood transfusions. This condition, sometimes called
acquired
hemochromatosis, is often treated with medicine. Too
much iron can have an effect on many organs in the body.

Infections

The transmission of viral infections,
such as
hepatitis B or C or
HIV, through blood transfusions has become very rare
because of the safeguards enforced by the U.S. Food and Drug Administration
(FDA) for the collection, testing, storage, and use of blood. The risk of
infection from a blood transfusion is higher in less developed countries, where
such testing may not happen and paid donors are used.

It is
possible for blood to be contaminated with bacteria
or parasites. Bacterial contamination can happen during or after donation. Donated blood might have a parasitic infection. Transfusion with blood that has bacteria or parasites can result
in a systemic infection. But this risk is small.

The risk of a bacterial infection in donated blood is small because of the precautions taken in drawing
and handling blood. There is a greater risk of
bacterial infection from transfusions with platelets. Unlike most other blood
components, platelets are stored at room temperature. If any bacteria are
present, they will grow and cause an infection when the platelets are used for
transfusion.

Receiving a Blood Transfusion

Before you receive a
blood transfusion, your blood is tested to
determine your blood type. Blood or blood components
that are compatible with your
blood type are ordered by the doctor. This blood may
be retested in the hospital laboratory to confirm its type. A sample of your
blood is then mixed with a sample of the blood you will receive to check that
no problems result, such as red blood cell destruction (hemolysis) or clotting.
This process of checking blood types and mixing samples of the two blood
sources is called typing and crossmatching.

Before actually giving
you the transfusion, a doctor or nurse will examine the label on the
package of blood and compare it to your blood type as listed on your medical
record. Only when all agree that this is the correct blood and that you are the
correct recipient will the transfusion begin. Giving you the wrong blood type
can result in a mild to serious
transfusion reaction.

If you have banked
your own blood in preparation for surgery (autologous donation), typing and
crossmatching is not needed. But the doctors and nurses still examine the label
to confirm that it is the blood you donated and that you are the right
recipient. For more information on this option, see:

Sometimes a doctor will recommend that you take
acetaminophen (such as Tylenol),
antihistamines (such as Benadryl), or other medicines
to help prevent mild reactions, like a fever or
hives, from a blood transfusion. Your doctor will treat
a more severe reaction if one occurs.

To receive the transfusion,
you will have an intravenous (IV) catheter inserted into a vein. A tube
connects the catheter to the bag containing the transfusion, which is placed
higher than your body. The transfusion then flows slowly into your vein. A
doctor or nurse will check you several times during the transfusion to watch
for a transfusion reaction or other problem.

Artificial Blood

Experts are trying to create artificial blood or blood replacements. Blood replacements being
studied include oxygen-carrying chemicals (such as perfluorocarbon emulsions)
and cell-free
hemoglobin—the portion of the red blood cell that
carries oxygen. There are several advantages to blood replacements.

Blood replacement products can be stored for
long periods of time. Human blood must be used within a few weeks of being
donated.

Blood replacement products can be stored at room
temperature. Human blood must be kept refrigerated until
used.

There is no risk of a
transfusion reaction caused by mismatched blood
type.

Blood replacement products can be sterilized, eliminating the
risk for infection.

The blood replacement products being tested still have
problems. For example, blood replacement products can interfere with blood
tests, are more quickly removed from the body, and are less efficient oxygen
carriers.

Several of these products are being developed. But their
use, after they are approved, will probably be limited to emergencies involving
severe blood loss caused by serious accidents.

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